California Code, Revenue and Taxation Code - RTC § 20605

(a) The postponement of property taxes pursuant to this chapter shall not affect the obligation of a borrower to continue to make payments to a lender with respect to an impound, trust, or other type of account described in Section 2954 of the Civil Code which was established prior to the effective date of subdivision (b).

(b) Except where required by federal law or regulation and notwithstanding Sections 7153.2 and 7153.8 of the Financial Code,  1 or in the case of a loan which is made, guaranteed, or insured by a federal government lending or insuring agency requiring the borrower to make payments to a lender with respect to an impound, trust, or other type of account described in Section 2954 of the Civil Code, or where this subdivision would impair the obligations of a loan agreement executed prior to the effective date of this subdivision, no lender shall require a borrower to maintain an impound, trust or other type of account with regard to taxes once such borrower has elected to postpone such taxes pursuant to this chapter and has first submitted to such lender evidence of tax postponement.  Any payments made by such borrower, prior to the time of submission of such evidence of tax postponement, to such an impound, trust or other type of account with regard to taxes for any such period, if not previously used in payment or partial payment of such taxes, shall be refunded to such borrower within thirty days thereafter.